1. Field of the Invention
This invention relates to a two-cycle heat-insulating engine which actuates intake valves and exhaust valves for opening and closing by electromagnetic force.
2. Description of the Prior Art
Conventionally, a valve mechanism which constitutes electrically intake/exhaust valves and actuates them electrically as a valve mechanism of an internal combustion engine is disclosed, for example, in Japanese Patent Laid-Open No. 183805/1983. The valve mechanism of this internal combustion engine includes a detector for detecting the operational condition of the internal combustion engine and actuates the intake and exhaust valves on the basis of the detection signal of the detector. The detector for detecting the operational conditions of the internal combustion engine is accomplished by detecting a rotation state of a crank shaft or by detecting an acceleration opening. The operation of the intake and exhaust valves by the electrical motion means is accomplished by regulating the opening degree of the valve portions in response to the operational conditions of the internal combustion engine such as the intake state of a fuel and an exhaust state of an exploded and burnt matter.
In the operations of gasoline engines and Diesel engines in general, the cycle of the four operations, i.e., an intake stroke, a compression stroke, a combustion stroke and an exhaust stroke, is repeated. Among them, it is only the combustion stroke where power is generated and torque is applied to a crank shaft. In the other three states, rotation is effected by the force of intertia. Two kinds of systems, that is, a four-cycle engine and a two-cycle engine, exist as the operation principle of each of these strokes. Incidentally, in the two-cycle engine, the intake stroke and the exhaust stroke are effected at part of the combustion stroke and the compression stroke and one cycle is completed in the two strokes of the piston or in other words, one revolution of the crank shaft. Accordingly, since the number of combustion strokes or the number of times of explosion is twice in the two-cycle engine in comparison with the four-cycle engine, the output becomes about 1.5 times that of the four-cycle engine at the same exhaust quantity.
In a heat-insulating engine having the heat-insulating structure wherein the cylinder head and the combustion chambers defined by cylinders formed in the cylinder block are made of a heat-insulating material, a ceramic material, or the like, volume efficiency drops due to high heat generated inside each cylinder and the engine output drops. The reason is as follows. Since the cylinder head and the upper part of the cylinder have the heat-insulating structure, the upper part and wall surface of each combustion chamber attain a high temperature and fresh air sucked into the cylinder receives the heat from inside the cylinder or from the wall surface and is heated and undergoes expansion so that volume efficiency drops. Moreover, the intake air quantity sucked into the combustion chamber is reduced by 20% or more by the influences of the wall surface which is at the high temperature.
In engines having the two-cycle operation, when the exhaust port is opened and the exhaust gas is discharged through the exhaust port for air exchange, a pressure wave or a pulse wave occurs inside the cylinder and purges the exhaust gas. Accordingly, the fresh air flows into the negative pressure zone generated at the trailing stream portion of this exhaust gas from the lower part of the cylinder but since the lower part of the cylinder does not attain such a high temperature as the cylinder head, the fresh air is not much affected by the wall surface temperature at the lower part of the cylinder. This provides the advantage particularly in the heat-insulating engine in that if the fresh air is sucked from the lower part of the cylinder by effecting the two-cycle engine operation, the scavenging air quantity or the intake air quantity is not reduced.
On the other hand, the temperature of the exhaust gas in the heat-insulating engine is very high. Therefore, if the intake valves and the exhaust valves are disposed in the cylinder head and are adjacent to one another as they are in a four-cycle operation engine, the intake ports are more likely to be affected by the thermal influences of the exhaust ports and exhaust gas so that the intake air undergoes expansion due to the thermal influences and the intake air quantity drops drastically.